1. Field of the Invention
This invention relates to photoelectric transducer elements, and more particularly to a photoelectric transducer element usable in devices for measuring object distance or for automatically focusing optical instruments in such a way that a light is projected from the device onto the object. Reflected light is received along with ambient light due to the sun light and/or artificial illumination, and is capable of producing output signals representing the projected light component and the ambient light component in a form distinguishable from each other.
2. Description of the Prior Art
The photoelectric transducer elements are selective because their selecting means relies on the MOS gate which had a large loss when ON and has been necessarily constructed in a form using a charge or CCD-like form.
A charge storing type light receiving element is shown in U.S. Pat. No. 3,999,192. The aforesaid U.S. Pat. No. 3,999,192 uses a charge storing type light sensor device having a sensor element receptive to reflected light and first and second charge storing portions each of which comprises two charge storing elements, as the aforesaid photoelectric light receiving means, wherein the projected light from the light projecting means disappears for a predetermined cycle. The aforesaid first and second control gate portions are controlled corresponding to the disappearance cycle of the projected light, whereby the charges generated on the respective sensor elements with and without the light being projected are applied to and stored on the respective charge storing elements in the first and second charge storing portions, separate from each other. The the accumulated charge on each of the elements in the first and second charge storing portions is taken out in appropriate timing. Then, the electrical signal difference obtained by accumulated charges on each pair of elements, which are related to each other with respect to each sensor element in those first and second charge storing portions, is obtained through a respective difference amplifier. Upon detection of either coincidence or disagreement between the two difference amplifier outputs, the focusing lens is moved to an adjusted position based on the detection signal, thereby focusing. Such a difference type amplifier is constructed with two light receiving elements. Based on the signals from the photoelectric transducing portions of the two light receiving elements, the position and distance of the object is measured. For example, when utilized in a photographic camera, the distance the focusing lens must be moved is computed. By this computation, it is possible to set up the focusing lens at a sharp focal point. Also, since the focusing lens is moving, when the in-focus condition is detected, the focusing lens can be stopped. In the light receiving device using such difference type amplifiers as described above, however, the gating control accuracy of each gate is required to increase.
The closest prior art known to Applicants is U.S. Pat. No. 4,274,735 and, in particular, FIG. 2 thereof. In the referenced patent, the gate elements for the memory elements (C1, C5) are constructed by the field effect transistors (GA1, GA1') having no function of amplification, while in the present invention the gate elements are constructed by the amplifying transistors (Ex. 6, 7). With this distinction, the present invention can obtain the high S/N ratio.
A first object of the present invention is to provide a photoelectric transducer element usable in a distance measuring device in which the reflected light of projected light by the light emitting means and reflected light of the ambient light such as sun light and artificial illumination are received, and the light received is subjected to photoelectric conversion so that the photoelectric transducing elements are obtained based on the aforesaid projected light and the ambient light. A photoelectric transducing signal is produced based on the projected light. Thereby the distance can be measured with great accuracy by the output signal of the photoelectric transducer element.
A second object of the present invention is to provide a photoelectric transducer element with the above feature and to provide components with many variations of the aforesaid changeover means, whereby the photoelectric transducer element is applicable to many fields and is suited for various purposes.
A further object is to provide a photoelectric transducer element which can produce an output of high sensitivity and high S/N ratio in a current mode of reduced loss.